// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "net/quic/crypto/crypto_framer.h"

#include <memory>

#include "base/strings/stringprintf.h"
#include "net/quic/crypto/crypto_protocol.h"
#include "net/quic/quic_data_reader.h"
#include "net/quic/quic_data_writer.h"

using base::StringPiece;
using std::pair;
using std::vector;

namespace net {

namespace {

    const size_t kQuicTagSize = sizeof(uint32_t);
    const size_t kCryptoEndOffsetSize = sizeof(uint32_t);
    const size_t kNumEntriesSize = sizeof(uint16_t);

    // OneShotVisitor is a framer visitor that records a single handshake message.
    class OneShotVisitor : public CryptoFramerVisitorInterface {
    public:
        OneShotVisitor()
            : error_(false)
        {
        }

        void OnError(CryptoFramer* framer) override { error_ = true; }

        void OnHandshakeMessage(const CryptoHandshakeMessage& message) override
        {
            out_.reset(new CryptoHandshakeMessage(message));
        }

        bool error() const { return error_; }

        CryptoHandshakeMessage* release() { return out_.release(); }

    private:
        std::unique_ptr<CryptoHandshakeMessage> out_;
        bool error_;
    };

} // namespace

CryptoFramer::CryptoFramer()
    : visitor_(nullptr)
    , error_detail_("")
    , num_entries_(0)
    , values_len_(0)
{
    Clear();
}

CryptoFramer::~CryptoFramer() { }

// static
CryptoHandshakeMessage* CryptoFramer::ParseMessage(StringPiece in)
{
    OneShotVisitor visitor;
    CryptoFramer framer;

    framer.set_visitor(&visitor);
    if (!framer.ProcessInput(in) || visitor.error() || framer.InputBytesRemaining()) {
        return nullptr;
    }

    return visitor.release();
}

bool CryptoFramer::ProcessInput(StringPiece input)
{
    DCHECK_EQ(QUIC_NO_ERROR, error_);
    if (error_ != QUIC_NO_ERROR) {
        return false;
    }
    error_ = Process(input);
    if (error_ != QUIC_NO_ERROR) {
        DCHECK(!error_detail_.empty());
        visitor_->OnError(this);
        return false;
    }

    return true;
}

// static
QuicData* CryptoFramer::ConstructHandshakeMessage(
    const CryptoHandshakeMessage& message)
{
    size_t num_entries = message.tag_value_map().size();
    size_t pad_length = 0;
    bool need_pad_tag = false;
    bool need_pad_value = false;

    size_t len = message.size();
    if (len < message.minimum_size()) {
        need_pad_tag = true;
        need_pad_value = true;
        num_entries++;

        size_t delta = message.minimum_size() - len;
        const size_t overhead = kQuicTagSize + kCryptoEndOffsetSize;
        if (delta > overhead) {
            pad_length = delta - overhead;
        }
        len += overhead + pad_length;
    }

    if (num_entries > kMaxEntries) {
        return nullptr;
    }

    std::unique_ptr<char[]> buffer(new char[len]);
    QuicDataWriter writer(len, buffer.get());
    if (!writer.WriteUInt32(message.tag())) {
        DCHECK(false) << "Failed to write message tag.";
        return nullptr;
    }
    if (!writer.WriteUInt16(static_cast<uint16_t>(num_entries))) {
        DCHECK(false) << "Failed to write size.";
        return nullptr;
    }
    if (!writer.WriteUInt16(0)) {
        DCHECK(false) << "Failed to write padding.";
        return nullptr;
    }

    uint32_t end_offset = 0;
    // Tags and offsets
    for (QuicTagValueMap::const_iterator it = message.tag_value_map().begin();
         it != message.tag_value_map().end(); ++it) {
        if (it->first == kPAD && need_pad_tag) {
            // Existing PAD tags are only checked when padding needs to be added
            // because parts of the code may need to reserialize received messages
            // and those messages may, legitimately include padding.
            DCHECK(false) << "Message needed padding but already contained a PAD tag";
            return nullptr;
        }

        if (it->first > kPAD && need_pad_tag) {
            need_pad_tag = false;
            if (!WritePadTag(&writer, pad_length, &end_offset)) {
                return nullptr;
            }
        }

        if (!writer.WriteUInt32(it->first)) {
            DCHECK(false) << "Failed to write tag.";
            return nullptr;
        }
        end_offset += it->second.length();
        if (!writer.WriteUInt32(end_offset)) {
            DCHECK(false) << "Failed to write end offset.";
            return nullptr;
        }
    }

    if (need_pad_tag) {
        if (!WritePadTag(&writer, pad_length, &end_offset)) {
            return nullptr;
        }
    }

    // Values
    for (QuicTagValueMap::const_iterator it = message.tag_value_map().begin();
         it != message.tag_value_map().end(); ++it) {
        if (it->first > kPAD && need_pad_value) {
            need_pad_value = false;
            if (!writer.WriteRepeatedByte('-', pad_length)) {
                DCHECK(false) << "Failed to write padding.";
                return nullptr;
            }
        }

        if (!writer.WriteBytes(it->second.data(), it->second.length())) {
            DCHECK(false) << "Failed to write value.";
            return nullptr;
        }
    }

    if (need_pad_value) {
        if (!writer.WriteRepeatedByte('-', pad_length)) {
            DCHECK(false) << "Failed to write padding.";
            return nullptr;
        }
    }

    return new QuicData(buffer.release(), len, true);
}

void CryptoFramer::Clear()
{
    message_.Clear();
    tags_and_lengths_.clear();
    error_ = QUIC_NO_ERROR;
    error_detail_ = "";
    state_ = STATE_READING_TAG;
}

QuicErrorCode CryptoFramer::Process(StringPiece input)
{
    // Add this data to the buffer.
    buffer_.append(input.data(), input.length());
    QuicDataReader reader(buffer_.data(), buffer_.length());

    switch (state_) {
    case STATE_READING_TAG:
        if (reader.BytesRemaining() < kQuicTagSize) {
            break;
        }
        QuicTag message_tag;
        reader.ReadUInt32(&message_tag);
        message_.set_tag(message_tag);
        state_ = STATE_READING_NUM_ENTRIES;
    case STATE_READING_NUM_ENTRIES:
        if (reader.BytesRemaining() < kNumEntriesSize + sizeof(uint16_t)) {
            break;
        }
        reader.ReadUInt16(&num_entries_);
        if (num_entries_ > kMaxEntries) {
            error_detail_ = base::StringPrintf("%u entries", num_entries_);
            return QUIC_CRYPTO_TOO_MANY_ENTRIES;
        }
        uint16_t padding;
        reader.ReadUInt16(&padding);

        tags_and_lengths_.reserve(num_entries_);
        state_ = STATE_READING_TAGS_AND_LENGTHS;
        values_len_ = 0;
    case STATE_READING_TAGS_AND_LENGTHS: {
        if (reader.BytesRemaining() < num_entries_ * (kQuicTagSize + kCryptoEndOffsetSize)) {
            break;
        }

        uint32_t last_end_offset = 0;
        for (unsigned i = 0; i < num_entries_; ++i) {
            QuicTag tag;
            reader.ReadUInt32(&tag);
            if (i > 0 && tag <= tags_and_lengths_[i - 1].first) {
                if (tag == tags_and_lengths_[i - 1].first) {
                    error_detail_ = base::StringPrintf("Duplicate tag:%u", tag);
                    return QUIC_CRYPTO_DUPLICATE_TAG;
                }
                error_detail_ = base::StringPrintf("Tag %u out of order", tag);
                return QUIC_CRYPTO_TAGS_OUT_OF_ORDER;
            }

            uint32_t end_offset;
            reader.ReadUInt32(&end_offset);

            if (end_offset < last_end_offset) {
                error_detail_ = base::StringPrintf("End offset: %u vs %u", end_offset,
                    last_end_offset);
                return QUIC_CRYPTO_TAGS_OUT_OF_ORDER;
            }
            tags_and_lengths_.push_back(std::make_pair(
                tag, static_cast<size_t>(end_offset - last_end_offset)));
            last_end_offset = end_offset;
        }
        values_len_ = last_end_offset;
        state_ = STATE_READING_VALUES;
    }
    case STATE_READING_VALUES:
        if (reader.BytesRemaining() < values_len_) {
            break;
        }
        for (const pair<QuicTag, size_t>& item : tags_and_lengths_) {
            StringPiece value;
            reader.ReadStringPiece(&value, item.second);
            message_.SetStringPiece(item.first, value);
        }
        visitor_->OnHandshakeMessage(message_);
        Clear();
        state_ = STATE_READING_TAG;
        break;
    }
    // Save any remaining data.
    buffer_ = reader.PeekRemainingPayload().as_string();
    return QUIC_NO_ERROR;
}

// static
bool CryptoFramer::WritePadTag(QuicDataWriter* writer,
    size_t pad_length,
    uint32_t* end_offset)
{
    if (!writer->WriteUInt32(kPAD)) {
        DCHECK(false) << "Failed to write tag.";
        return false;
    }
    *end_offset += pad_length;
    if (!writer->WriteUInt32(*end_offset)) {
        DCHECK(false) << "Failed to write end offset.";
        return false;
    }
    return true;
}

} // namespace net
